Apparatus for purging or bleeding fluid lines, particularly those intended for use in jet aircraft, generally include a bleed valve permanently attached to the fluid line and a separate valve actuator releasably connected to the bleed valve which is operative, in a valve open position, to open the valve and purge or bleed fluid from the line. After the bleed or purge operation is completed, the valve actuator is removed and the bleed valve remains with the fluid line.
One common deficiency of bleed apparatus of the type described above is that no safety mechanism is provided to prevent engagement or disengagement of the valve actuator and bleed valve when the valve actuator is in the valve open position. If the valve actuator is in a valve open position upon connecting or removing it from the bleed valve, leakage of fluid from the fluid line is virtually certain to occur. This can be particularly dangerous where caustic or other hazardous fluid is being transmitted by the fluid line.
Another problem with bleed or purge apparatus such as described above involves inadvertent damage to the valve member of the bleed valve. Most bleed valves of the type utilized in a bleed/purge application include a one-way valve member such as a ball which is spring-biased against a seat to place the valve in a closed position. The valve actuator is moved to the valve open position to disengage this ball from the seat to open the valve. In many bleed apparatus designs, the valve actuator can be tightened down into a valve open position with such force as to damage the spring or other means used to bias the valve member of the bleed valve into a normally closed position. After a period of time, the spring or other biasing means can be weakened to a point where it fails to return the ball to a seated, closed position and thus permits leakage of the fluid from the valve.
A still further limitation of many apparatus for bleeding or purging fluid from a fluid line is the size and weight of the bleed valve portion of the apparatus. This is of particular concern in applications such as the fluid lines in jet aircraft wherein the bleed valves must be as small and lightweight as possible. Because the bleed valve is permanently attached to the fluid line, the bulky or heavy bleed valves of many prior art apparatus cannot be utilized in applications such as in jet aircraft.